1. Technical Field
The invention relates generally to radio frequency (RF) modules, and more particularly, to RF modules capable of self-calibration.
2. Related Art
Wireless communications has gradually become a basic function of electronic devices, especially for portable ones. An electronic device capable of performing wireless communications generally includes a radio frequency (RF) module operative to handle RF signals. The RF module includes several electronic components. These components are frequently manufactured through mass production and as a result may not conform to their specifications precisely. For example, as compared with an ideal model, an RF module may be different on a transmission path as a whole, or on some sub-bands of the transmission path. As a result, the power level of the transmitted RF signal may deviate from the desired power level. Furthermore, as compared with the ideal model, the RF module may be different on a receiving path as a whole, or on only some sub-bands of the receiving path. As a result, the actual loss caused by the receiving path may deviate from the expected amount.
In response, several calibration mechanisms have been proposed. However, some of the mechanisms require too many additional components to be used, and hence significantly increase the overall hardware costs. Some of the mechanisms calibrate only a part of an RF signal path, which can be a transmission or receiving path, but does not compensate for the variance attributable to the rest part of the RF signal path. For example, if the RF module includes an antenna switch module (ASM) that allows a single antenna to be shared by several RF signal paths, the ASM will be a source of power/loss variations but the power/loss variations attributable to the ASM are seldom calibrated.